There is a free tool supporting all types of RAR cracking (with or without header encryption) called cRARk and it's heavily optimized for all CPU architectures, like AVX2, AVX, XOP, AES-NI for Intel Haswell and AMD Bulldozer processors.
It supports only 1 thread for CPU (no multicore) and only one GPU or CPU (not at the same time)
Also, no pause/resume.
Latest v5.1 supports x64 and CUDA http://www.crark.net/download/crark51.rar for Nvidia cards and x64 and OpenCL http://www.crark.net/download/crark51-ocl.rar for AMD
For Intel GPUs you have to download previous 5.0c version http://www.crark.net/download/crark50-ocl.rar which works on Win 10 x64 latest driver.
Some benchmarks on RAR3 without header encryption:
Radeon 5750 ~2500 pass/s
Intel HD4600@1.5GHz ~760 pass/s
Core i7-4790 (AVX2) ~700 pass/s (Single thread)
Nvidia GT610 ~700 pass/s
Core i5-2400 (AVX) ~300 pass/s (Single thread)
Core 2 Duo@2.86GHz (SSE2) ~200 pass/s (Single thread)
It supports only 1 thread for CPU (no multicore) and only one GPU or CPU (not at the same time)
Also, no pause/resume.
Latest v5.1 supports x64 and CUDA http://www.crark.net/download/crark51.rar for Nvidia cards and x64 and OpenCL http://www.crark.net/download/crark51-ocl.rar for AMD
For Intel GPUs you have to download previous 5.0c version http://www.crark.net/download/crark50-ocl.rar which works on Win 10 x64 latest driver.
Some benchmarks on RAR3 without header encryption:
Radeon 5750 ~2500 pass/s
Intel HD4600@1.5GHz ~760 pass/s
Core i7-4790 (AVX2) ~700 pass/s (Single thread)
Nvidia GT610 ~700 pass/s
Core i5-2400 (AVX) ~300 pass/s (Single thread)
Core 2 Duo@2.86GHz (SSE2) ~200 pass/s (Single thread)